CN113784660B - Method and apparatus for measuring airway resistance - Google Patents

Abstract

An apparatus for measuring a lung function parameter using quiet exhalation, the apparatus having a flow tube, a shutter, a controllable latch, a flow sensor, a pressure sensor, a latch controller, and a check valve, the flow tube having a mouthpiece end and an outlet, the shutter covering the outlet of the flow tube; the controllable latch closes and releases the shutter, the flow sensor is used for measuring the flow in the flow tube after the shutter is released, the pressure sensor is used for measuring the pressure in the flow tube before the shutter is released, the latch controller is connected to the pressure sensor and the controllable latch; a check valve is disposed in the flow tube or shutter for allowing inhalation when the shutter is closed, enabling the device to be used throughout at least one inhalation and exhalation cycle.

Description

Method and apparatus for measuring airway resistance

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application Serial No. 62/824,393, filed on March 27, 2019, the contents of which are incorporated herein by reference.

Technical Field

The present application relates to medical diagnostic and monitoring devices, and more particularly to devices for measuring respiratory parameters such as airway resistance.

Background technique

The diagnosis of respiratory diseases and the monitoring of their progression are based on measuring respiratory parameters. One of such medically valuable parameters is airway resistance.

The interrupter or shutter measurement method is one of the techniques for determining airway resistance that requires minimal cooperation from the subject. With this method, the subject breathes through a breathing tube. At a certain moment, usually during exhalation, the opening of the breathing tube is briefly closed by the shutter. In a short period of time (typically about 100ms-150ms) after closing, the air pressure in the mouth and breathing tube increases to a level that is assumed to correspond to the alveolar pressure at the moment of airflow interruption. The measured value of the airflow just before the shutter is closed and the accumulated pressure are used to determine the airway resistance. A variant of the interruption technique, known as the "open" interruption method, uses a different measurement sequence. The flow rate is not measured before the airflow is interrupted but shortly after the shutter is opened. In this method, a longer interruption period provides a more complete balance between the alveolar and mouth pressures, which improves the accuracy of the airway resistance measurement. According to this method, interruptions are made only during the inspiratory phase and in the middle part of the inspiratory phase. Mouth pressure is measured immediately before opening, while airflow is averaged during a period of 15 ms-35 ms after opening the shutter (Eur. J. Respir. Dis., 1982, Vol. 63, pp. 449-458 (198263, 449-458), K. van der Plas, P. Vooren "The "opening" interruptor. A new variant of a technique formeasuring respiratory resistance").

Another variation of the interruption during breathing maneuver technique is described in applicant's pre-grant U.S. patent publication US 2016/256073, in which the subject begins breathing into a flow tube that is initially closed by a shutter. Applicants refer to this device and technique as relaxed occluded exhalation monitoring (REOM). After the accumulated pressure exceeds a certain threshold, the shutter is opened, and the flow spike is measured during 100ms-150ms after the shutter is released. The airway resistance of the upper and lower airways is determined by analyzing the shape of the flow waveform. Airway resistance measurements can be made after a single expiratory cycle that includes the occlusion phase and a brief flow spike after occlusion.

Summary of the invention

Applicants have found that in the case of REOM, there may be some hesitation between the user or patient due to inhaling without properly placing the device mouthpiece in the mouth, and then making a move to place the mouthpiece in the mouth before starting a non-forced exhalation. The following improvements to this technology are proposed in the present invention.

Switching from a single exhalation (with one interruption event) to spontaneous breathing (when interruptions occur multiple times at the start of each subsequent exhalation) makes the breathing maneuver easier for the subject. The subject can maintain his or her lip shape and continue to inhale and exhale in a relaxed or non-effortful manner. Spontaneous breathing is more natural than single exhalation when the subject is concentrating on a single trial and unconsciously may try to control his or her exhalation, which can result in an occlusion phase that is too fast or too slow, as well as distortion of the flow waveform caused by the additional effort that is different from the effort applied during full spontaneous breathing.

In prior art REOM devices, the shutter may be hinged or simply fall away from the flow tube. When the shutter is operated in a continuous mode, it will return to the occluded position. Applicants have found that when the shutter is arranged to provide little impedance to the flow measurement after release for a period of about 200ms after release, the measurement is not affected by the shutter. At this point, if the shutter begins to return during exhalation, any resistance to the expiratory flow is not a problem. Once exhalation stops and inhalation begins, the shutter has plenty of time to return to the occluded position and be latched.

In some embodiments, a device for measuring lung function parameters using quiet exhalation is provided, the device having a flow tube, a shutter, a controllable latch, a flow sensor, a pressure sensor, a latch controller, and a check valve, the flow tube having a mouthpiece end and an outlet, the shutter covering the outlet of the flow tube; the controllable latch closes and releases the shutter, the flow sensor is used to measure the flow in the flow tube after the shutter is released, the pressure sensor is used to measure the pressure in the flow tube before the shutter is released, and the latch controller is connected to the pressure sensor and the controllable latch; the check valve is arranged in the flow tube or the shutter to allow inhalation when the shutter is closed, so that the device can be used throughout at least one inhalation and exhalation cycle.

Multiple shutter openings at the beginning of each exhalation can improve measurement accuracy by:

- Obtain interruption flow/pressure data from multiple interruption events;

- reject certain disruption events if forced efforts are detected, or if the flow waveform is distorted due to phonation or other artifacts;

- averaging the airway resistance measured over multiple interruption events, or

-Averaging multiple post-occlusion flow waveforms, and further calculating airway resistance from the averaged flow waveforms.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood through the following detailed description of embodiments of the present invention with reference to the accompanying drawings, in which:

FIG. 1A shows a prior art design of a flow tube with a shutter for airway resistance measurement that uses a pitot tube for measuring expiratory flow and a single sensor for measuring both flow and pressure.

Figure 1B shows a prior art design of a flow tube with a shutter for airway resistance measurement, which prior art design uses a flow sensor port and shutter arrangement for measuring expiratory flow and a single sensor for measuring both flow and pressure, where a cross-section of the tube at the shutter position along line A-A is shown in Figure 1C.

FIG. 2A schematically presents a design of a flow tube with the shutter closed at the beginning of exhalation.

FIG. 2B schematically presents a design of a flow tube with the shutter open during exhalation.

FIG. 2C schematically presents a design of the flow tube with the shutter closed and the valve open during inhalation.

FIG. 2D schematically presents a variant design of a flow tube with the shutter closed during inspiration, wherein the flow tube has an additional port and sensor for measuring inspiratory flow.

FIG. 3 shows a design of a shutter with an inclined axis of rotation.

Figure 4 shows the mouthpiece of the flow tube.

FIG. 5A shows one embodiment of a device having an alternative location of a valve integrated with the flow tube.

FIG. 5B shows a schematic block diagram of one embodiment of the device in combination with a smart phone or computing device.

FIG. 6 is a schematic flow chart describing the operation of the apparatus.

FIG. 7 shows the output signal of the pressure sensor at the end of the occlusion phase and at the beginning of the post-occlusion flow spike after shutter release.

FIG8 schematically presents a variant design of a flow tube similar to FIG2D , in which the shutter is closed during inhalation, wherein the flow tube has a shutter guard;

FIG. 9 is a front view of the embodiment of FIG. 8 showing the shutter guard.

Detailed ways

A prior art design of a flow tube with a shutter for a respiratory device for airway resistance measurement is shown in FIGS. 1A to 1C . The device performs the measurement of airway resistance based on one interruption event at the beginning of a single exhalation. The position of the shutter at the end of the post-occlusion spike is unimportant and indeterminate. The shutter can be fully open or closed. The only requirement is that after the shutter is released, the shutter remains open during a first time period of about 100ms-150ms to provide the undistorted flow waveform required to calculate the airway resistance. However, it should be understood that the shutter does not interfere with the measurement of the post-occlusion flow spike.

The switch from a single interruption event based mode of operation of the breathing device to one based on multiple interruptions at the beginning of the subsequent exhalation cycle may provide easier, more natural and more convenient breathing operation. The subject may breathe spontaneously in a relaxed manner without focusing on a single exhalation and trying to control the expiratory effort. Therefore, the results may be more representative of the patient's true vital capacity.

In order to achieve an operating mode of the breathing apparatus based on multiple interruption events, the shutter may be configured to provide: a) free and unobstructed exhalation immediately after shutter release and during relaxation of inspiration, b) blockage of the flow tube at the beginning of exhalation and during the occlusion phase. This means that the shutter may return to its initial closed position at the beginning of each exhalation.

FIG. 2A shows one of the possible embodiments of a flow tube 1 with a shutter 4. When the flow tube 1 is blocked, the position of the shutter 4 corresponds to the start of exhalation. The shutter 4 may have one or more openings 10 closed by a check valve 12, which may be made of a soft and flexible material similar to rubber or silicone. A magnet 15 may attract a metal fragment 14 of the shutter 4, such as a ferromagnetic metal clip or insert, to prevent the shutter from opening during the occlusion period when the pressure in the flow tube 1 increases until the desired threshold is reached. If the shutter 4 is made of a suitable metal material, a separate fragment 14 is not required. Other types of latch mechanisms may be used to hold and release the shutter 4. The flexible check valve membrane 12 may block the opening 10 in the shutter 4 at this stage. In addition, it should be understood that the check valve 12 may be replaced by any other device that controls the opening to allow airflow during inspiration and prevent airflow during exhalation, such as using an electronically controlled valve that operates based on sensor readings.

After the accumulated pressure exceeds a predetermined threshold, the solenoid 16 can push the shutter 4 to release it from the magnet 15. The increase in the distance between the magnet 15 and the metal fragment 14 of the shutter 4 quickly reduces the magnetic attraction force and further opens the shutter 4 by the compressed air accumulated during the occlusion stage. When other forms of latching mechanisms are used, different triggers or release mechanisms can be used (for example, an electromagnet can be used instead of the magnet 15, and the release mechanism of the shutter 4 can include de-energizing the electromagnet).

Full opening of the shutter 4 may take about 10 ms, with minimal distortion of the air flow. FIG7 shows a typical output signal of a sensor 8 measuring the pressure in the air channel 2 of the flow tube 1. The positive signal corresponds to the pressure during the occlusion phase (zero flow), while the negative signal corresponds to the flow after the shutter is released. It may take about 8 ms to open the shutter 4 and reduce the accumulated pressure to zero. When the port 7 is arranged downstream of the baffle or in a pitot tube, the expiratory air flow through the tube 1 causes a negative pressure and a negative output signal of the sensor 8. The maximum absolute value of the signal may be reached about 10 ms after the shutter is opened and corresponds to the peak flow.

As shown, the shutter 4 is a single flap type valve that opens outwardly and is therefore pushed by and moves with the air flow leaving the flow tube 1. It will be appreciated that more than one flap may be arranged to provide a releasable occlusion at the end of the flow tube 1. The movement of the flap and the released air does not adversely affect the measurement of the flow in the tube 1 by the sensor 8.

It will be understood that the measuring device may include a circuit for controlling latch release, pressure and flow in the measuring tube 1 from the sensor 8 readings, and optionally calculating values such as airway resistance and/or lung compliance from the readings. Such a circuit is described in the applicant's pre-grant patent publication US 2016/256073 (the specification of which is incorporated herein by reference). For example, this may include a microcontroller associated with the sensor 8, and data processing may be completed using an associated program or application on a connected device (e.g., Bluetooth) (such as a smart phone or other convenient computing device, etc.). This may allow the cost of data processing to be removed from the measuring device. As described in more detail below with reference to FIG. 6, the recording of such measurements may involve multiple "tests" or exhaled collection measurements performed when the user inhales and exhales normally without a compulsion, and the data may be averaged and/or compiled as needed.

In some embodiments, the airway resistance measurement method involves measuring the flow rate within a range of about 100ms-150ms after the shutter is opened. After this time interval, the position of the shutter 4 may not be critical to the measurement. Preferably, once the shutter 4 is released, the shutter 4 should not prevent the subject's spontaneous exhalation. Figure 2B shows the shutter 4 at a maximum opening position that can be limited by a buffer or damper 11. When the shutter 4 swings open, the buffer 11 can provide an abutment for the shutter 4 to determine the maximum opening angle of the shutter 4. The opening angle can be an important parameter of the device and will be discussed below. It should be understood that the buffer 11 can take a variety of different forms to provide the function of limiting the opening angle.

An external return force may be applied to the shutter 4 to push it to its initial closed position. This force may be generated by a spring or by using electrostatic and magnetic principles. As shown in the present embodiment, gravity may also be used. After the buffer 11 is opened and collides with the buffer 11, the shutter 4 returns to its initial position and may block the opening of the flow tube 1, preventing normal exhalation of the subject. To exclude this possibility, the solenoid 16 remains energized to prevent the shutter 4 from contacting the magnet 15 and to leave a wide enough gap between the shutter and the flow tube for exhalation. If desired, the buffer 11 may also provide some elastic energy to return the shutter 4 to the closed position, thus, for example, assisting gravity or a spring mechanism.

The onset of inspiration can result in a significant negative pressure within the flow tube 1, which can be detected by the sensor 8. After the inhalation is detected, the solenoid 16 can be immediately de-energized and the shutter 4 can stick to the magnet 15 (latch closed). The check valve 12 opens, allowing the subject to inhale through the flow tube 1. FIG. 2C shows the position of the shutter 4 during inspiration.

After the subject completes inspiration and begins exhalation, the positive pressure within flow tube 1 closes check valve 12 and a new occlusion phase begins.

FIG2D shows an embodiment in which an additional port 7' can be added before the flow baffle located before port 7. Port 7' can be positioned as shown so that a sensor 8" can be used to measure the inspiratory flow. Sensor 8" is shown as being connected to measure the differential pressure across the baffle in the flow tube, and sensor 8" will then measure both the inspiratory flow and the expiratory flow. It will be understood that other arrangements for measuring inspiration are possible, and that the measurement of inspiration is optional if only the expiratory flow is of interest. By measuring the inspiratory flow and the expiratory flow in one or more respiratory cycles, the device can measure further lung parameters, such as tidal volume, slow vital capacity, etc. When measuring slow vital capacity (SVC), the baffle can be kept open if necessary. Different arrangements of flow sensors can be used. A single sensor can be used to measure forward and reverse flow, while another sensor can be used to measure pressure. Measurement of flow/volume parameters of breathing may require fixing the baffle 4 in a permanent open position and temporarily disabling the airway resistance measurement mode.

FIG3 shows a front view of an embodiment in which the shutter 4 with the hinge 9 rotates about an axis 6 which is inclined at an angle α relative to the direction of the gravitational acceleration. The dynamics of the opening and closing of the shutter 4 may depend on the following parameters:

- angle α;

-Mass of shutter 4:

- The position of the buffer 11 which limits the opening angle of the shutter 4 .

Without the hinge, it will be appreciated that the shutter would need to be placed in a closed position prior to use, however, the check valve allows the patient to begin using the device by first completing a quiet inspiration before quietly exhaling. Quiet exhalation and the stability of the resulting measurements can be improved by starting with an inspiration.

In the embodiment of FIG. 3 , when SVC is performed, the flow tube can be rotated so that gravity keeps the shutter 4 open.

By adjusting these three construction parameters, the following conditions can be met: The time interval between the shutter opening and its collision with the flow tube can exceed the observation time required to measure the post-occlusion flow waveform, which is about 150 ms. If the collision of the shutter with the flow tube occurs faster than the mentioned time, the flow disturbance caused by the collision can interfere with the device measurement.

In one specific case of the device embodiment, the damper or buffer 11 can be positioned so that the opening angle of the shutter 4 is about 150°. The angle α between the axis of rotation and the direction of gravity acceleration can be selected to be about 75°. The experimental measurement time interval between the shutter opening and its collision with the flow tube is about 250ms, which is long enough to perform undistorted flow waveform measurements to determine airway resistance.

After the user starts to inhale, negative pressure is generated inside the flow tube 1 , and this negative pressure can be detected by the sensor 8 .

It will be appreciated that gravity may be used in place of or in addition to the use of a light spring or biasing member to return the shutter 4 towards the closed position. If gravity or biasing does not cause the shutter 4 to seal against the end of the flow tube 1, it will be appreciated that subsequent inhalation will assist in closing the shutter until the check valve 12 opens, and even then, during inhalation, a small negative pressure will exist inside the tube 1 which will assist in keeping the shutter 4 closed.

After inhalation is detected, the solenoid 16 can be de-energized (normally, the release mechanism is only temporarily triggered to cause the shutter to release) and the shutter can be attached to the magnet 15. The soft membrane of the check valve 12 can bend inward due to the negative pressure in the flow tube 1 generated during inhalation, and the hole 10 in the shutter 4 can be opened, allowing air to flow through the flow tube 1. The check valve 12 can be opened until the end of the inhalation. When the subject begins to exhale, the check valve 12 closes and the occlusion phase begins.

FIG4 shows an example of a mouthpiece 3 connected to the air channel 2 of the flow tube 1. The mouthpiece 3 includes an optional tongue depressor 5 to fix the position of the tongue, preventing the tongue from possibly blocking the opening of the flow tube 1, distorting the airflow and adversely affecting the measurement of the respiratory device. Such a mouthpiece 3 can be made disposable. It can also be an integrated part of the flow tube 1, and the entire flow tube 1 joined with the mouthpiece 3 can be made disposable. The mouthpiece 3 can also be integrated with a bacterial filter.

Figure 5A shows an alternative embodiment of the device in which a check valve 12 closes the opening 10 in the body of the flow tube 1. In this configuration of the device, it is not necessary to attach the check valve 12 to the shutter 4 and to form the hole 10 in the shutter 4.

FIG5A also shows the option that the sensor 8 can be separated into two different sensors 8 and 8' for exhaled flow and pressure, respectively, rather than using one sensor operable for both flow and pressure. FIG5A also shows that the latch controller can be included in the device for controlling the release of the latch based on the pressure measurement. FIG5A also shows that a data transceiver (such as a wireless link, a cable link, etc.) can be used to transmit data from the sensor 8 to another device for processing.

Although not shown, external processing means can be used to monitor the pressure during shutter occlusion and to signal the latch to release. If the inspiratory flow is also to be measured, a flow sensor 7', 8" will need to be arranged at port 10.

In FIG5B , a system is shown comprising the device in combination with a computing device, such as a smart phone. The computing device may include a processor, a memory storing a computer program for the device 1 , a data transceiver for communicating with the device 1 , and optionally a network interface for transmitting data and/or receiving settings from a remote party. The device may include a microcontroller or microprocessing semiconductor unit which may include a wired or wireless transceiver for communicating with the computing device. Functions such as shutter control, acquisition control using an indicator on the device or a user interface on the computing device, data acquisition and storage, raw and/or compliance calculations, etc., can therefore be implemented as needed using the processing power of the device or the processing power of the computing device.

In the exemplary embodiment of FIG. 5B , the device is configured to control shutter release based on a pressure threshold value, the value of which may be set, for example, by software of the computing device and/or a setting of a user interface. The computing device may include software for communicating the results from the device to a healthcare professional (HCP), and if desired, the shutter release pressure setting may be set by the HCP. Alternatively, shutter release may be controlled from the computing device, in which case the device transmits pressure readings to the computing device every few milliseconds.

FIG. 5B also shows that the computing device can perform a flow spike waveform consistency analysis. This analysis is optional and can also be performed by the processor of the device if desired. The consistency analysis can be a comparison of flow spike waveforms (e.g., post-occlusion flow data, typically up to about 150ms after peak flow) relative to each other. Because measurements can be made at each exhalation, multiple waveforms are easily acquired. When a waveform is significantly different from other waveforms, perhaps due to compulsion, coughing, phonation, etc., the waveform can be ignored. Then, many consistent waveforms can be used and their associated flow tube pressures when the occlusion is released for measurement.

Optionally, the device or smartphone can signal to the user that data collection has ended because a period of time or number of exhalations has elapsed and/or because a number of consistent waveforms have been collected. A stop signal (e.g., audible or visual) can be provided by an indicator on the device or by a smartphone or computer.

The software in the device or computer may also be arranged to measure slow vital capacity. The measurement may start with the user selecting the measurement, or the device and/or computer may indicate to the user that this measurement will start. The user inhales slowly and completely, followed by a slow exhalation, in which the air is completely exhaled from the lungs using muscle force. The device measures the flow during this exhalation and the volume of air in the exhalation may be recorded as an SVC measurement. If the device also measures inspiratory flow, the SVC measurement may involve measuring the volume of inspiration and exhalation to confirm the SVC measurement by using both inspiration and exhalation data. Therefore, the presence of the shutter and its release pressure will not adversely affect the SVC measurement.

While it may be best to separate the systems between the device and the smartphone as a way to provide a better user interface and reduce the cost of the device, it should be understood that the device may incorporate a user interface and may incorporate network connectivity so that the device may be completely independent of any smartphone or computer.

FIG. 6 shows a block diagram illustrating one possible embodiment of the operation of the breathing apparatus during a breathing cycle.

First, when the subject inhales, the shutter 4 is closed and the check valve 12 is opened (see FIG. 2C ). The transition from inhalation to exhalation is accompanied by a change in pressure inside the flow tube 1 from negative to positive, which can be detected by the sensor 8. The check valve can be automatically closed at the beginning of exhalation.

In the next step, the sensor 8 can measure the accumulated pressure during the occlusion phase. When the accumulated pressure inside the flow tube 1 reaches a predetermined threshold, the solenoid 16 can be energized. The solenoid 16 can push the shutter 4, resulting in a rapid opening of the flow tube 1. As mentioned above, other latching mechanisms can be used without departing from the teachings of the present disclosure.

After the shutter 4 is released and when the shutter is widely opened, the post-occlusion flow can be measured over a period of about 100ms-150ms. Based on these data, the airway resistance can be calculated.

An external return force may be applied to the shutter 4 after it has been opened in order to return the shutter to its initial closed position. This force may be generated, for example, by a spring or by gravity. Other sources of external return force (like static electricity or magnetism) are also possible. A second force counteracting the return force prevents complete closing of the shutter 4 so that the patient can continue to exhale. The second reaction force may be generated, for example, by the shutter 16. The shutter 16 continues to be energized so as to maintain a gap between the shutter and the edge of the flow tube 1. Typically, when the shutter is partially closed, during exhalation, the pressure inside the flow tube 1 is positive.

The transition from exhalation to inspiration is accompanied by a change in air pressure from positive to negative inside the flow tube 1. After such a transition is detected, for example by the sensor 8, the reaction force can be turned off (for example, the shutter 16 is de-energized) and the shutter 4 can be completely closed by an external return force. The shutter 4 can be glued to the magnet 15. The negative pressure inside the flow tube 1 can cause the check valve 12 to bend inward, causing the hole 10 to open and allowing air to flow through the tube 1 during inspiration.

The use of post-occlusion non-forced expiratory flow waveforms and occlusion pressure to calculate airway resistance and/or lung compliance is described in the applicant's pre-grant patent publication US 2016/256073 published on September 8, 2016. At this stage, the measured raw data of the interruption event can (optionally) be transferred to a computer or smartphone. Alternatively, if the electronic hardware supports this mode of operation, data can be continuously transmitted during all stages of the respiratory cycle.

As the computer or smartphone receives the measurement data, decisions can be made in real time about the acceptability of the measurement. For example, an abnormally short occlusion time may indicate that excessive expiratory force is being applied, which may be unacceptable during non-forced airway resistance measurements. Distortions of the post-occlusion flow spike, such as those caused by phonation or other artifacts, can also be detected. Such data can be rejected. After performing several interruption events, the average flow spike waveform can be calculated. Those flow waveforms that deviate from the average waveform by more than a certain percentage and do not meet the repeatability criteria can be excluded from further analysis.

As one of the possible options, airway resistance can be determined for each single interruption event. Then, the average airway resistance can be calculated during the execution of multiple interruption events. Alternatively, the average post-occlusion flow waveform can be calculated while excluding single interruption events that do not meet the repeatability criteria. Then, the airway resistance can be calculated based on the average flow waveform.

If the required number of acceptable interruption events are generated and measured, the measurement procedure can be completed automatically.

The shutter can be made of a thin plastic or metal material and is therefore fragile if knocked open and impacted by a foreign object. In Figures 8 and 9, a protective ring is shown as being added at the end of the flow tube, which can be used to prevent the shutter from being bumped due to careless storage. The protective ring is arranged so as not to significantly interfere with the movement of the shutter or the air flow discharged from the flow tube. Although a ring has been shown, it should be understood that the shutter guard can take different forms, for example it can include multiple protrusions arranged around the far end of the flow tube. This alternative arrangement can provide lower interference with the airflow at the far end of the flow tube. The shutter guard can be further designed to protect the shutter in its closed position and open position.

Claims (18)

1. A device for measuring lung function parameters, comprising: a flow tube having a mouthpiece end and an outlet; a shield plate, the shield plate covering the outlet of the flow tube; a hinge connecting the shutter to the flow tube so that the shutter opens outwardly in a manner configured to be pushed by and move with airflow exiting the flow tube; wherein the hinge is mounted on the flow tube, wherein the axis of rotation of the hinge is angled relative to gravitational acceleration such that after the shutter opens outwardly with the airflow exiting the flow tube to provide a plurality of shutter openings, gravity causes the shutter to return to a closed position; a controllable latch that closes and releases the shutter; a flow sensor for measuring the flow in the flow tube after the shutter is released; wherein the shutter having mass and the angle of the hinge are arranged to provide a low impedance for flow measurement in the flow tube after the shutter is released within a time period of 200 ms after the shutter is released, so that the flow being measured in the flow tube is not affected by the shutter; a pressure sensor for measuring pressure in the flow tube prior to release of the shutter; a latch controller connected to the pressure sensor and the controllable latch; and A check valve is disposed in the flow tube or the shutter for allowing inspiration when the shutter is closed, so that the device can be used throughout at least one inspiration and exhalation cycle. 2. The device according to claim 1 further comprises a calculator connected to the flow sensor and the pressure sensor for calculating the lung function parameter. 3. An apparatus according to claim 2, wherein the calculator uses data from the flow sensor up to 150ms from peak flow after the shutter is released to calculate the lung function parameter. 4. The apparatus of claim 2, wherein the calculator calculates the lung function parameter from a plurality of interruption events at the beginning of subsequent exhalation cycles. 5. The device according to claim 4, wherein the lung function parameter is airway resistance. 6. The device according to claim 1, further comprising a data transmitter for transmitting data from the device to a computing device so as to calculate the lung function parameter from the data. 7. The apparatus of claim 6, wherein the data comprises the flow sensor measurements from peak flow to up to 150 ms from peak flow after the shutter is released. 8. The apparatus of claim 1, wherein the flow sensor is configured to additionally measure inspiratory flow. 9. The device of claim 1, wherein the flow sensor is a first flow sensor for measuring exhalation, and the device further comprises a second flow sensor for measuring inhalation. 10. The apparatus of claim 1, wherein the latch controller is connected to the controllable latch and the pressure sensor and is configured to release the shutter at the beginning of exhalation when pressure in the flow tube has begun to increase without forced effort. 11. The device of claim 1, wherein the latch controller releases the controllable latch at a predetermined pressure. 12. The device of claim 11, wherein the predetermined pressure is defined by an external computing device. 13. The device of claim 1, wherein the check valve is disposed in the shutter. 14. The apparatus of claim 1 wherein expiratory flow is measured for a full exhalation, the apparatus further comprising a calculator connected to the flow sensor for calculating slow vital capacity from the full exhalation after the shutter is released. 15. The apparatus of claim 1, further comprising a shutter guard mounted to a distal end of the flow tube. 16. The device of claim 1, further comprising a biasing member that assists in returning the shutter toward the closed position. 17. A system for measuring lung function parameters, comprising The device for measuring lung function parameters according to claim 1, wherein the device comprises a data transceiver; and A computing device comprising a corresponding data transceiver and a memory storing a computer program for communicating with the device and providing a user interface for controlling the device. 18. The system of claim 17, wherein the computing device further comprises a calculator for calculating a lung function parameter from data in at least one interruption event at the beginning of a subsequent exhalation cycle.